1. Field of the Invention
The present invention relates to an optical probe for producing a tomogram of a specimen from the information of light scattered in the specimen by radiating the specimen with low-coherence light.
2. Related Art Statement
In recent years, in the case where living-body tissue is diagnosed, as a device which can gain optical information regarding the inside of the tissue, OCT (Optical•Coherence•Tomography) which produces a tomogram of a specimen by the use of low-coherence light has been disclosed in, for example, PCT Japanese Translation Patent Publication No. 6-511312.
However, regarding the conventional optical probe, there are disadvantages in that, for example, since when a tube-shaped sheath is curved, a flexible shaft is contacted with the inner surface of the tube-shaped sheath, the relative length between the tube-shaped sheath and the flexible shaft is changed, and consequently, when the tip clearance between the tip inner surface of the tube-shaped sheath and the tip surface of the tip unit is small, rotation performance is degraded due to butting of the sheath tip portion and the inside rotor and, therefore, a proper OCT image cannot be produced.
When this tip clearance (gap) is large, since the relative length between the tube-shaped sheath and the flexible shaft is changed as described above, the position of the light exit•entrance portion of the tip unit is changed. Consequently, there are problems in that, for example, it becomes difficult for an operator to ascertain the light exit position and, therefore, operating ease for the operator during observation is degraded.
Regarding the conventional optical probe, since the tip clearance which is the interval between the inner surface of the tip side seal portion and the tip portion of a member holding an optical element in the sheath lumen has been minimized, precision in sheath length has been required and, therefore, productivity has been degraded. The length of the sheath is changed depending on, for example, use with bending, change with time, and friction during insertion due to reuse.
There have been disadvantages in that, for example, when the tip clearance has been large, operating ease for the operator during observation has been degraded, and when the tip clearance has been small, rotation performance has been degraded due to butting of the sheath tip portion and the inside rotor and, therefore, it has not been possible to produce a proper OCT image.
Regarding the conventional optical probe, in the case where a probe is curved, for example, the probe is inserted through a channel for forceps of an endoscope and is inserted into a body cavity, a support portion of the optical element at the tip, etc., are rotated while being in contact with the inner side of a sheath and, therefore, the inner surface of the sheath may be damaged, or the sheath outer surface may be damaged due to friction between the channel for forceps inner surface and the sheath outer surface by insertion operation into the channel for forceps. Consequently, sometimes, optical characteristics of the part, where observation light has been made to exit or enter the optical element faced, have been degraded and, therefore, the optical performance of the sheath has been maintained by making the sheath exchangeable as disclosed in, for example, Japanese Patent Application No. Hei 10-266753.
However, since the lengths of the probe main bodies to be inserted into the sheath have varied depending on individual pieces, it has been necessary to produce while the lengths of the sheaths have been adjusted in accordance with probes on a piece basis, or to produce while the length tolerance of the probe main body is made to become closer. This has caused further reduction of productivity of the sheath.